Effect of nifedipine on coronary hemodynamics in patients with left anterior descending coronary occlusion.

The mechanisms responsible for the beneficial effects of calcium channel antagonists in patients with effort angina were investigated by studying the coronary hemodynamic responses of the anterior left ventricular region before and after administration of nifedipine in 13 patients whose left anterior descending coronary artery was filled by flow from collateral vessels. Nifedipine was given bucally in a dose (10 or 20 mg) that decreased aortic pressure 5 mm Hg or more. Nifedipine increased collateral flow (regional thermodilution) in only three patients (p = NS), but consistently decreased coronary resistance in the left ventricular anterior region (p less than 0.05). Anterior region myocardial oxygen consumption did not change after nifedipine administration. Lactate metabolism was evaluated in eight patients: values were abnormal in four patients before nifedipine; after nifedipine, values remained abnormal in three of these patients and became abnormal in one other. During atrial pacing stress, angina occurred in all patients before nifedipine and at the same or lower heart rate in nine patients after nifedipine. After nifedipine administered at the same rate that induced angina during the control period, collateral flow and myocardial oxygen consumption were usually lower (both p less than 0.05), but anterior region coronary resistance was unchanged compared with control values. Lactate metabolism was not usually improved. Thus, although nifedipine maintained collateral flow while aortic pressure decreased, no consistent beneficial effect on pacing-induced angina was seen.